ASTM_D_5454_-_11e1.pdf

Designation:D5454111Standard Test Method forWater Vapor Content of Gaseous Fuels Using ElectronicMoisture Analyzers1This standard is issued under the fixed designation D5454;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1NOTEFig.1 was editorially updated in July 2011.1.Scope1.1 This test method covers the determination of the watervapor content of gaseous fuels by the use of electronic moistureanalyzers.Such analyzers commonly use sensing cells basedon phosphorus pentoxide,P2O5,aluminum oxide,Al2O3,orsilicon sensors piezoelectric-type cells and laser based tech-nologies.1.2 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D1142 Test Method for Water Vapor Content of GaseousFuels by Measurement of Dew-Point TemperatureD1145 Test Method for Sampling Natural Gas(Withdrawn1986)3D4178 Practice for Calibrating Moisture Analyzers3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 capacitance-type cellthis cell uses aluminum coatedwith Al2O3as part of a capacitor.The dielectric Al2O3filmchanges the capacity of the capacitor in relation to the watervapor present.Silicone cells also operate on this principal byreporting a capacitance change when adsorbing or desorbingwater vapor.3.1.2 electrolytic-type cellthis cell is composed of twonoble metal electrode wires coated with P2O5.Abias voltage isapplied to the electrodes,and water vapor chemically reacts,generating a current between the electrodes proportional to thewater vapor present.3.1.3 piezoelectric-type cell sensor consists of a pair ofelectrodes which support a quartz crystal(QCM)transducer.When voltage is applied to the sensor a very stable oscillationoccurs.The faces of the sensor are coated with a hygroscopicpolymer.As the amount of moisture absorbed onto the polymervaries,a proportional change in the oscillation frequency isproduced.3.1.4 laser-type cell consists of a sample cell with anoptical head mounted on one end and a mirror mounted on theother;however,some models will not need a mirror to reflectthe light wavelength emitted from the laser.The optical headcontains a NIR laser,which emits light at a wavelength knownto be absorbed by the water molecule.Mounted,the laser is adetector sensitive to NIR wavelength light.Light from the laserpasses through the far end and returns to the detector in theoptical head.A portion of the emitted light,proportional to thewater molecules present,is absorbed as the light transits thesample cell and returns to the detector.3.1.5 water contentwater content is customarily expressedin terms of dewpoint,F or C,at atmospheric pressure,or thenonmetric term of pounds per million standard cubic feet,lb/MMSCF.The latter term will be used in this test methodbecause it is the usual readout unit for electronic analyzers.One lb/MMSCF=21.1 ppm by volume or 16.1 mgm/m3ofwater vapor.Analyzers must cover the range 0.1 to 50lb/MMSCF.3.1.6 water dewpointthe temperature(at a specified pres-sure)at which liquid water will start to condense from thewater vapor present.Charts of dewpoints versus pressure andwater content are found in Test Method D1142.4.Significance and Use4.1 Water content in fuel gas is the major factor influencinginternal corrosion.Hydrates,a semisolid combination of hy-drocarbons and water,will form under the proper conditions1This test method is under the jurisdiction ofASTM Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.05 on Determination ofSpecial Constituents of Gaseous Fuels.Current edition approved July 11,2011.Published July 2011.Originallyapproved in 1993.Last previous edition approved in 2004 as D545404.DOI:10.1520/D5454-11E01.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 causing serious operating problems.Fuel heating value isreduced by water concentration.Water concentration levels aretherefore frequently measured in natural gas systems.A com-mon pipeline specification is 4 to 7 lb/MMSCF.This testmethod describes measurement of water vapor content withdirect readout electronic instrumentation.5.Apparatus5.1 The moisture analyzer and sampling system will havethe following gen